Camshaft adjusting device

ABSTRACT

A camshaft adjusting device having a vane-type adjuster which includes 
     a rotatably drivable stator which is connectable to a first camshaft; and 
     a rotor which is rotatably supported in the stator and is connectable to a second camshaft, 
     a plurality of radially inwardly projecting projections, which divide an annular space between the stator and the rotor into multiple pressure chambers, being provided on the stator; and 
     a plurality of outwardly projecting vanes, which divide the pressure chambers into oppositely acting working chambers, being provided on the rotor, 
     a pressure medium being applicable to the working chambers to optionally adjust the rotor with respect to the stator via a central valve, 
     the stator being rotatably fixedly connected or connectable to the first camshaft via the central valve.

This claims the benefits of German Patent Application DE 102013210283.6, filed Jun. 4, 2013 and hereby incorporated by reference herein.

The present invention relates to a camshaft adjusting device.

BACKGROUND

Camshaft adjusting devices include a camshaft and a vane-type adjuster which, in its basic configuration, has a stator which is drivable by a crankshaft and a rotor which is rotatably fixedly connected to the camshaft. An annular space is provided between the stator and the rotor, which is divided into a plurality of pressure chambers by projections which are rotatably fixedly connected to the stator and project radially to the inside, the pressure chambers each being divided into two working chambers having different directions of action by a vane which projects radially to the outside from the rotor. Depending on the application of a pressure medium to the working chambers, the rotor is then adjusted with respect to the stator, and the camshaft is adjusted with respect to the crankshaft, in the “advance” or “retard” direction. The working chambers are delimited by the side surfaces of the projections and the vane and by a first sealing surface on the rotor and a second sealing surface on the stator, against which the projections and the vanes rest by their front surfaces, forming a seal.

To apply pressure to the working chambers, for example a central valve having a movable valve body may be provided, which has a plurality of control edges and pressure medium channels through which the pressure medium may be optionally introduced into the working chambers as a function of the position of the valve body. The central valve is furthermore used to clamp the rotor to the camshaft by the fact that, on the outside, the central valve rests against an external side surface with the aid of a radial flange and is screwed into a female thread of the camshaft with the aid of a threaded section. A frictionally engaged connection between the camshaft and the rotor, and between the rotor and the central valve, is thus formed, by means of which the adjusting forces necessary for the adjusting movement of the camshaft are transmitted. In this specific embodiment, the central valve is also referred to as the central screw.

According to one refinement of a camshaft adjusting device of this type, the stator may be additionally rotatably fixedly connected to a second camshaft, so that by adjusting the rotor with respect to the stator, an adjustment of the rotation angle of the two camshafts with respect to each other is also possible as an alternative or in addition to the rotation angle adjustment of the camshaft with respect to the crankshaft. The camshafts may be inserted into each other and be situated concentrically to each other.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a camshaft adjusting device for adjusting the rotation angle between two camshafts, which, as far as possible, should have a simple structure and be cost-effective to manufacture.

The present invention provides a camshaft adjusting device having a vane-type adjuster which includes a rotatably drivable stator which is connectable to a first camshaft; and a rotor which is rotatably supported in the stator and is connectable to a second camshaft, a plurality of radially inwardly projecting projections, which divide an annular space between the stator and the rotor into multiple pressure chambers, being provided on the stator; and a plurality of outwardly projecting vanes, which divide the pressure chambers into oppositely acting working chambers, being provided on the rotor, a pressure medium being applicable to the working chambers to optionally adjust the rotor with respect to the stator via a central valve.

The present invention provides that the stator is rotatably fixedly connected or connectable to the first camshaft via the central valve. Due to the proposed approach, the camshaft adjusting device has a very simple structure in that the central valve is also used to connect the stator to the first camshaft in addition to its actual function of controlling the pressure medium flow. This results in two very short force transmission paths involving a very small number of components, namely a first force transmission path from the stator to the first camshaft via the central valve, and a second force transmission path from the rotor to the second camshaft. In the event that the stator is drivable by a crankshaft, the first camshaft is in rotatably fixed connection to the crankshaft, while the rotation angle of the second camshaft is adjustable with respect to the crankshaft and the first camshaft.

It is furthermore proposed that the central valve may be integrally connected to the stator or to a component which is rotatably fixedly connected thereto. The proposed integral connection is advantageous in this respect, since it is able to transmit comparatively large forces in a small installation space. Moreover, the integral connection is very cost-effective to produce, since the components require very little or no machining at all for this purpose. In particular, there is no need for cutting operations or installation spaces and wall thicknesses of the components which have been necessary previously, e.g., in the case of threads.

The connection between the central valve and the stator may be produced particularly easily and cost-effectively if the component which is rotatably fixedly connected to the stator is a cover of the stator. The proposed connection is advantageous from a manufacturing perspective, since the cover is very easily accessible from the outside so that the central valve may be connected to the cover on an outer surface, e.g., using a welded connection. The central valve may be first connected to the cover of the camshaft adjusting device in a preceding operation and subsequently assembled as a module together with the cover.

It is furthermore proposed that the central valve may be connected to the first camshaft by a mated connection which is form-fitted in the circumferential direction. Since the connection between the central valve and the first camshaft is provided within the camshaft adjusting device, this connection is, in principle, more difficult to implement and, in particular, more difficult to assemble. The proposed mated connection which is form-fitted in the circumferential direction may be implemented without any special tools or skills simply by plugging the two components into each other, so that this approach to the present connection is particularly advantageous for assembly.

The form-fitted connection in the circumferential direction may have a clearance in the axial direction, with the aid of which an axial tolerance compensation may be implemented. The assembly may also be further simplified thereby, since the components of the camshaft adjusting device may be assembled more easily due to the clearance.

It is alternatively proposed that the central valve mat be connected or connectable to the first camshaft in the axial direction without clearance. The proposed approach provides the advantage that the central valve may thereby also be used to transmit axial forces in the sense of a simplified axial bearing of the first camshaft.

The central valve may furthermore have a radial flange situated on a front side, which projects radially to the outside. Due to the proposed radial flange, a type of stop may be created, with the aid of which the assembly of the camshaft adjusting device is simplified. In particular, the insertion depth of the central valve into a tubular end section of the second camshaft may be limited thereby.

It is furthermore proposed that the central valve may be integrally connected to the sealing cover in a radially outer section of the radial flange. For practical purposes, the radial flange forms a protruding wall section, which may be used to fasten the central valve. It is particularly advantageous that the integral connection may thereby be situated at the greatest possible distance to a radial inner valve surface provided on the central valve for a movable valve body provided in the central valve. Since the integral connection is manufactured by melting on the materials, for example during welding, a large amount of heat is locally introduced into the central valve, which should not result in a disadvantageous influencing of the valve surface. Due to the integral connection provided on the radial outer section of the radial flange, the distance between the integral connection and the valve surface may be increased, and the heat introduction into the valve surface during the production of the integral connection may be reduced thereby.

It is furthermore proposed that the radial flange may be dimensioned in such a way that it overlaps the side surface of the rotor. Due to the proposed dimensioning of the radial flange, an additional stop is created for limiting the insertion movement of the central valve into the through-opening.

It is furthermore proposed that the second camshaft may have a tubular end section, by means of which it extends into the through-opening between the rotor and the central valve, and elongated openings extending in the circumferential direction are provided in the tubular end section, through which the pressure medium may be introduced from the central valve into the working chambers. Due to the connection of the central valve to the cover of the stator and the connection of the second camshaft to the rotor, the tubular end section of the second camshaft executes a relative movement with respect to the central valve fastened to the cover of the stator during an adjustment. Since the central valve is situated in the tubular end section of the second camshaft, and an inflow and outflow of the pressure medium via the central valve must be possible at the same time, the proposed elongated openings oriented in the circumferential direction are particularly advantageous, since this facilitates an inflow and outflow of the pressure medium through the tubular end section of the second camshaft over a certain angle range of the adjusting movement.

It is furthermore proposed that the central valve may have a base body and a valve body which is movable within the base body, and a cavity having a volume which is variable by the movement of the valve body is provided between the valve body and the base body, and the cavity is connected to the surroundings of the camshaft adjusting device with the aid of a venting line. According to the present invention, the central valve is connected to the first camshaft with the aid of the immobile base body. Due to the proposed approach, the base body may be individually designed for fastening to the first camshaft, a cavity provided for this purpose being connected to the surroundings by the venting line in such a way that the volume present therein is not compressed and does not interfere with the movement of the valve body. In particular, the base body may thereby be fastened in a camshaft designed as a solid shaft with a central section. The spring for pretensioning the valve body, which in this case is supported on the base body and spring-loads the valve body in the exit direction from the cavity, may be provided right in the cavity.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention is explained in greater detail below on the basis of one preferred exemplary embodiment.

FIG. 1 shows a sectional representation of a camshaft adjusting device according to the present invention.

DETAILED DESCRIPTION

A sectional representation of a camshaft adjusting device having a vane-type adjuster which includes a rotor 1 and a stator 2 is apparent in FIG. 1. Stator 2 includes a driving surface, such as a toothing, radially on the outside, with the aid of which the valve-type adjuster is driven by an endless traction means during operation. The driving action may be carried out via a crankshaft of an internal combustion engine or another drive shaft. Stator 2 itself has an annular design and includes a plurality of projections 13 which project radially to the inside, in which a fastening opening 14 is provided for screwing two covers 3 and 4 which cover the stator at the side. If stator 2 has a cup-shaped design, only cover 3 is provided, which covers cup-shaped stator 2 at the side. Covers 3 and 4 and stator 2 form a rotatably fixed assembly, due to the screw connection. Projections 13 projecting radially to the inside extend up to a first sealing surface of rotor 1 and thereby divide an annular space present between rotor 1 and stator 2 into multiple pressure chambers. A plurality of vanes is furthermore provided on rotor 1, which extend up to a second sealing surface of stator 2 and thereby further divide the created pressure chambers into two oppositely acting working chambers. A pressure medium may be optionally applied to each working chamber through a pressure medium line via a central pressure medium circuit, the pressure medium from the working chambers to which pressure medium is not applied being fed back into a pressure medium reservoir. By applying the pressure medium to the working chambers of one direction of action, rotor 1 is rotated with respect to stator 2 either in the direction of rotation of stator 2 or counter to the direction of rotation of stator 2. To this extent, the vane-type adjuster corresponds to the prior art.

Rotor 1 has a central through-opening 11, into which second camshaft 5 extends via a tubular end section 9. Elongated openings 12, which are oriented in the circumferential direction, are provided on tubular end section 9. Second camshaft 5 is rotatably fixedly connected to rotor 1 via tubular end section 9, e.g., via one or multiple welded connections, an adhesive connection, a threaded connection or a press-fit connection.

A central valve 6 is furthermore provided, which has multiple through-openings 15 and a central cylindrical recess, in which a spring-loaded valve body 7 is movably guided, which has different control edges and through bore-holes. Central valve 6 also has a radial flange 8 on its front side, which projects radially to the outside and has a larger outer diameter than the inner diameter of through-opening 11. Central valve 6 is situated in tubular end section 9 of camshaft 5 and is integrally connected to cover 3 of stator 2 on the radial outside of radial flange 8, via a welded connection 10.

Welded connection 10 may be a circumferential, uninterrupted weld seam, which is implemented, for example, with the aid of a highly dimensionally accurate laser welded connection. The proposed arrangement of welded connection 10 on the radial outside of radial flange 8 is useful to the extent that it thereby has a greater distance to the valve surfaces between central valve 6 and tubular end section 9 or between valve body 7 and the cylindrical inner wall of central valve 6, so that the amount of heat introduced during welding results in less thermal deformation of the valve surfaces. Due to the overlapping between the front side of tubular end section 9 and the side surface of rotor 1 implemented by the larger outer diameter, radial flange 8 furthermore provides a stop which limits the insertion movement of central valve 6 into through-opening 11 of rotor 1 or into tubular end section 9 of camshaft 5, which may simplify assembly.

Central valve 6 is furthermore connected to a first camshaft 17 via a mated connection 18 which is form-fitted in the circumferential direction, mated connection 18 which is form-fitted in the circumferential direction being implemented by a dihedron in this case. Connection 18 has a clearance in the axial direction, by means of which a tolerance compensation may be implemented in the axial direction. Alternatively, a connection which has no clearance in the axial direction may be selected at this point, with the aid of which axial forces may be transmitted for axially supporting first camshaft 17.

In the illustrated specific embodiment of the present invention, central valve 6 is integrally connected to cover 3 of stator 2, and second camshaft 5 is connected to rotor 1, via tubular end section 9. When rotor 1 is adjusted with respect to stator 2, rotor 1, together with second camshaft 5 and tubular end section 9, executes a rotary motion with respect to central valve 6 fixedly attached to the stator and first camshaft 17. Due to elongated openings 12 oriented in the circumferential direction, the pressure medium may flow out of or into the working chambers via through-openings 15 of central valve 6 in the different angular positions of rotor 1.

The proposed integral connection between central valve 6 and cover 3 is thus advantageous, since no special preceding machining steps for the components are needed to create this connection, so that the manufacturing costs may be reduced. Moreover, the integral connection may be carried out in a very small installation space in a noticeably space-saving manner, since the integral connection is very strong in and of itself, and, to create the connection, only small, freely accessible surfaces must be present on the components to be connected.

In the present exemplary embodiment, the connection was described on the basis of an integral connection between central valve 6 and cover 3. In another assignment of the components, however, central valve 6 may also be integrally connected directly to stator 2 or rotor 1 and have the same advantages.

However, the described fastening of central valve 6 to cover 3 is particularly advantageous, since central valve 6 and cover 3 form surfaces which are particularly easily accessible from the outside, in particular due to radial flange 8 provided, on which the integral connection may be implemented. Furthermore, the described assignment results in a particularly simple configuration having two assemblies, namely a first assembly including cover 3 or stator 2 and rotatably fixedly connected central valve 6, and a second assembly including rotor 1 and camshaft 5 connected via the tubular end section.

Cover 3 may also be integrally connected to central valve 6 in a separate, preceding operation and then fastened to stator 2 as an assembly, rotor 1 being already connected to camshaft 5 during this operation. Cover 3, together with central valve 6 fastened thereto, is then inserted into tubular end section 9 of camshaft 5 and screwed to opposite cover 4 through fastening openings 14, via appropriate fastening screws.

Central valve 6 has a base body 22, on which the dihedron is provided on the front side in a central section for the purpose of creating form-fitted connection 18. Base body 22 is made of solid material on its end facing first camshaft 17, so that it may be easily provided with the central dihedron, which in this case is an extension of base body 22. Due to the shape of base body 22, a cavity 21 is present between base body 22 and valve body 7, so that valve body 7 may be pushed against base body 22 to control the pressure medium flow. A spring 23, which spring-loads valve body 7 in the exit direction from cavity 21, is provided in cavity 21. To prevent valve body 7 from thereby exiting base body 22, the latter is secured on the opposite front side of valve body 7 with the aid of a retaining ring 24 provided on base body 22.

Venting lines 19 and 20, which are fluidically connected to each other and also fluidically connected to cavity 21, are provided in base body 22 and in the two camshafts 5 and 17 and create a connection between cavity 21 and the surroundings of the camshaft adjusting device. This allows the pressure medium present in the cavity or the air present therein to escape into the surroundings when valve body 7 moves against the force of spring 23 or to flow into cavity 21 in the case of the opposite movement.

List of Reference Numerals

-   1 Rotor -   2 Stator -   3 Cover -   4 Cover -   5 Second camshaft -   6 Central valve -   7 Valve body -   8 Radial flange -   9 End section -   10 Welded connection -   11 Through-opening -   12 Elongated openings -   13 Projection -   14 Fastening opening -   15 Through-opening -   16 Dihedron -   17 First camshaft -   18 Connection -   19 Venting line -   20 Venting line -   21 Cavity -   22 Base body -   23 Spring -   24 Retaining ring 

What is claimed is:
 1. A camshaft adjusting device having a vane adjuster comprising: a rotatably drivable stator connectable to a first camshaft; a rotor rotatably supported in the stator and connectable to a second camshaft; a plurality of radially inwardly projecting projections dividing an annular space between the stator and the rotor into a plurality of pressure chambers and being provided on the stator; a plurality of outwardly projecting vanes dividing the pressure chambers into oppositely acting working chambers and being provided on the rotor; and a pressure medium being applicable to the working chambers to selectively adjust the rotor with respect to the stator via a central valve, the stator being is rotatably fixedly connected or connectable to the first camshaft via the central valve.
 2. The camshaft adjusting device as recited in claim 1 wherein the central valve is integrally connected to the stator or to a component rotatably fixedly connected to the stator.
 3. The camshaft adjusting device as recited in claim 2 wherein the component is a cover of the stator.
 4. The camshaft adjusting device as recited in claim 1 wherein the central valve is connected to the first camshaft via a mated connection form-fitted in the circumferential direction.
 5. The camshaft adjusting device as recited in claim 4 wherein the mated connection has a clearance in the axial direction.
 6. The camshaft adjusting device as recited in claim 1 wherein the central valve is connected or connectable to the first camshaft without clearance in the axial direction.
 7. The camshaft adjusting device as recited in claim 1 wherein the central valve has a radially outwardly projecting radial flange situated on the front side.
 8. The camshaft adjusting device as recited in claim 7 wherein the central valve is integrally connected to the sealing cover in a radially outer section of the radial flange.
 9. The camshaft adjusting device as recited in claim 1 wherein the second camshaft has a tubular end section extending into a through-opening between the rotor and the central valve; and the tubular end section has elongated openings extending in the circumferential direction, the pressure medium conductable through the elongated openings from the central valve into the working chambers.
 10. The camshaft adjusting device as recited in claim 1 wherein the central valve has a base body and a valve body movable in the base body; and a cavity having a volume, the volume being variable by the movement of the valve body is provided between the valve body and the base body, the cavity being connected to surroundings of the camshaft adjusting device via a venting line. 